This invention is concerned with novel basic zinc phosphite pigments and their method of preparation. These pigments are useful as tannin stain inhibitors in water and solvent based coating compositions for wood surfaces. The pigments also impart anticorrosive and mildew resistant properties to such coatings.
In the past, lead-based pigments such as basic lead silicate complexes and dibasic lead phosphite have been utilized in paints for inhibiting the tannin staining of wood surfaces such as cedar or redwood which are used extensively in roof and siding coverings for homes and other buildings. These pigments act to prevent the bleeding of tannin or other wood colorant from the wood surface through the coating film which would cause streaking and discoloration and thereby destroy the appearance and quality of the coating. Although the performance of these pigments are highly satisfactory, they suffer from the disadvantage that they are lead-based and therefore ecologically undesirable due to the inherent toxicity of the lead contained therein. As a result, industry is constantly seeking new substitutes for lead containing products which are non-toxic and at the same time exhibit the high performance characteristics of the lead products.
In view of the foregoing, it is an object of this invention to provide a substitute for lead-based tannin stain inhibitor pigments.
It is also an object of this invention to provide novel basic zinc phosphites having excellent efficiency as tannin stain inhibitors for wood surface coatings.
It is a further object of this invention to provide a novel process for preparing said basic zinc phosphites.